Electrical testing device



' E. H. BIRCHALL ELECTRICAL TESTING DEVICE Filed June 1, 1921 PatentedFeb. 24, 1925.

UNITED STATES PATENT ormce.

BENJAMIN H. BIRCHALL, F HIGHLAND PARK, PENNSYLVANIA, KSSIGNOR TOAMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL TESTING DEVICE.

Application filed June 1, 1921; Serial No. 474,119.

To alt/whom it may concern: as measured, will be approximately that Beit known that I, BENJAMIN H. BIR- which opposes the propagation of thevoice errant, a citizen of the United States, resiclcurrents.

ing at Highland Park, in the county of Another objectof this device isto pro- Delaware and State of Pennsylvania, have vide an arrangementwhereby the source of invented certain Improvements in Electricalalternating energy, which is connected to one Testing Devices, of whichthe following is a end of the circuit under test, may beconspecification. trolled at remote point upon the circuit Thlsinvention relates to electrical testing where the receiving device isconnected with 10 devices and particularly to means for the circuit.This not only enables one man determining the existence and location ofto operate the test set, but also limits the electrical unbalances insignaling circuits. period of application to the circuit of the For theproper operation of signaling cirtesting potential, since the test mancan units, and particularly of phantom telelisten inupon the circuit andcan control 15 phone circuits, it is: necessary that the sides from thelistening point the application of of the circuit shall be well balancedclecthe testing potential to the circuit under test. irically, that isto say, the resistance, induc- Other and further objects of thisinvenfiance, and capacity of the sides of a circuit tion will appearfrom the following descripshall be substantially the same. A111electrition, when read in connection with the at- 20 cal unbalancereduces the transmission tached drawing which shows one form oiefliciency of the circuit by causing cross-talk embodiment of theinvention. and increasing the susceptibility of the cir- In. thedrawing, 1, 2, 3 and lreprese11t'75 i-euit to interference from electricpower tour conductors constituting the lines L circuits, consequently itis desirable to and L which, for example, may be any two locateandremove as promptly as possible, pairs of signaling circuits, and, whenpropall causes of unbalance. erly connected constitute a phantom tele-One otrthe principal causes is high rephone circuit. R representsaresistance in sistance contacts in the twisted sleeve joints conductor1, which may be of any magniof line wires. It has been found that directtude. Such resistance may be created by an 30 current measurements,which it has been imperfectly twisted joint in a line wire, customaryheretofore to make, fail in many which causes a resistance unbalancebetween cases to accurately determine the magnitude 7 the sides of thecircuit. The approximate or position of these joints. This inherentlocation of such resistance unbalance having defect in direct currentmeasurements probbeen previously made from some central 35 ably resultsfrom the tendency of the current testing point, it is the object of theappli which flows during the period in which the cants invention to makea precise location measurement is being made, to change the ofthedefect. This has usually been made magnitude of the sleeve resistancethereby by connecting the source of testing potential, giving rise to afalse measurement, which is comprising the apparatus within the dottedgenerally lower than the actual resistance of lines X, with one end ofthe circuit under the joint to signaling current-s. It has been test andconnecting the other part of the found that the resistance which hasbeen testing apparatus go np 'ising the devices lowered by the processof measurement is within the dotted line Y, with the other end turns toits original value after the source of the circuit under test, so thatthe fault 45 of direct current has been disconnected. will lie betweenthe two points of connection. One Of the objec s of this invention s tThe source of testing potential comprises provideatesting system havingas its source the balanced, retardation coils and 6 1 of energy analternating current generating which are adapted to be connected withthe device, capable of producing current of ap conductors of the linecircuit by means oit' proximately the same-frequency as the voice leads40, 4 1, 42 and 43 equipped with clips currents transmitted overtelephone signal-- for fastening the leads to the conductors ingcircuits whereby the magnitude of the of the line circuit. Connected. inseries heresistance or other unbalance in the circuit, tween themid-points of the co ls, 5 and 6 the batteries 13, and B and the windingof relay 7. Controlled by relay 7 is relay 8, which when energized setsin operation the source of testing potential 9, and also short-circuitsthe line circuits L, and L with which the leads from the source ortesting potential may be connected. This short-circuiting of the linecircuits prevents unbalances in the line to the left of point A fromcausing a tone in the receiver at B, but the shortcircuiting of thecoils 5 and (S does not prevent the proper functioning of the coils withrespect to the oscillator current.

The source of alternating potential here shown is a type of harmonicvibrator. It comprises a carbon transmitter 10. the button of which isunder the control and influence of a vibrating reed which in turn iscontrolled by the magnets 11. The condenser 12 is connected in parallelwith the inductance 11 and another condenser 13 is connected in one ofthe conductors of the output circuit of the vibrator.

The apparatus within the dotted lines Y constitutes what may be termedthe receiving circuit. T, and T represent two repeating coils havingprimary windings 15 and 17 respectively and secondary windings 16 and 18respectively, each primary winding being divided in two halves.Connected between the two halves of each primary winding is a coil of apotentiometer, and the moving arm of each potentiometer is connectedwith the switch 21. The secondary coils 16 and 18 are'connected with theupper and lower contacts respectively of the switch 22, and the movingcontacts or blades of the said switch are in turn connected with thereceiver 23, and also with the contacts of switch 21. The primarywindings of the coils T, and T, are connected through the switches 19and 20 respectively with leads 41, 4 2 and 4.3 having clips connectedthereto in order that connections may readily be made with theconductors of the lines L, and L Associated with switch 21. is anotherswitch 2%, whose function is to control directly the operation of relay7 which in turn controls the application of the testing potential to thecircuit under test.

Having in mind the foregoing description of the apparatus, thisinvention will be better understood from the following description ofits mode of operation. Let it be assumed that the source of testingpotential is connected with the conductors of the circuits L, and L atsome junction point of the line such as a cable terminal, a loadingpoint, the end of a transposition section, or one end of any section ofline in which it is believed that unbalance exists. The receivingapparatus is connected to the other end of the section of the same linewith which the source of testing potential is coir nected, the apparatusbeing connected by fastening the test clips to the respectiveconductors. Since the coils 5 and 6 and the windings and 17 of the coilsT, and T are well balanced, it will be seen that no unbalance is createdby bridging these coils or windings across the line circuits andconsequently this may be done upon working circuits without causingcircuit interrup tions. By means of the receiver 23, the test man maylisten upon each of the side circuits and upon the phantom circuit inorder to determine whether these circuits are being used for thetransmission of signals. This is done by the proper manipulation of theswitches 19, 20, 21 and 22. Thus, when switch 19 is closed and switch 22is in its upper position, the receiver is connected to the side circuitL,. In a corresponding way, when switch is closed, and 22 in its lowerposition, the receiver is connected with the side circuit L and,furthermore, with switches 19, 20 and 21 closed, the receiver is bridgedacross the phantom circuit of the side circuits L, and L If the test manfinds the circuits idle, he will operate the key 24 which establishes acircuit from the upper contact of switch 24. midpoint of winding 15,over conductors 1 and 2, in parallel, through the windings of coil 5,batteries B, and B relay 7 wind ings of coil 6 and conductors 3 and 4 inparallel to the midpoint of windings 17 and thence to the contact of key24. This results in the operation of relay 7, which, in turn, causescurrent to flow from battery B, through a circuit embracing the windingof relay 8 and contact of relay 7. Through the closing of the contacts25 and 26, a circuit established from one side 01"" battery 13, contact25, the variable resistance carbon transmitter 10, winding 11, conta t26. to the other side of battery 13,. This sets in operation theharmonic vibrator 9, which by the action of its reed causes the varianceot resistance of the transmitter 10. The resulting oscillations areimpressed on the circuits L, and L over the conductors connected withthe inidpoints oi. coils 5 and 6. he closing of contacts 27 and 28 shortcircuits lines L, and L, and as stated prottwts the receiver agx-xiustthe ellects ot unbalaures in the lines to the left of point A. Thecurrents flowing through the conductors 1, 2, 3 and 4-, will be dividedin accordance with the resistances of the conductors and willsubsequently flow through the windings l5 and 17 of the coils T, and TIt a perfect balance existed on the side circuit, i. e. if no unbalance,such as for example R, existed in any conductor, no sound would be heardin the receiver when the resistance of each of the potentiometers 29 and30 is equally divided between the two wires of each side circuit. If anunbalance exists in one wire or resistance and inductance unbalance.

of the side circuit, due to the presence of an improperly twisted jointor other source of irregularity, such as R, a balanced condition canonly be obtained by adjusting the variable resistance of thepotentiometer connected with that circuit until no tone is perceptiblein the receiver'23, and the amount.

of change of the potentiometer will indicate the magnitude of theunbalance.

It a balance cannot be obtained, regardless of the extent of adjustmentof the potentiometer. it should be adjusted :tor minin'iuin tone.Experience in testing signaling circuits shows that when a .ininimun'itone is obtained with an equal division of resistance between the twowires the unbalance is due entirely to capacity or inductance; andturthermore if the minimum tone is obtained with an unequal division ofresistance, the faults include both resistance and capacity,

locate the position of a fault, the receiving circuit should beconnected with the line ciruits at a point nearer the source ofpotential and another test made similar to that aforedescribed. In thismanner the actual location oi. the trouble may be determined.

The foregoing description makes clear the method of testing forimbalances of the side circuits of a phantom group. My invention is notthus limited but is capable of measuring the imbalances existing in aphantom circuit and also in a non-phantomed circuit. Thus, in order tomeasure the unbalance eX- lsting in a phantom circuit represented forexample by the group of side circuits L and L the conductors I and 2should be short-circuited at both points A and B, and in like mannerconductors 3 and at should be similarly short-circuited. The connectinglead 40 should be connected with the shortcircuited conductors l and 2at A,'and lead -l-l should in a similar manner be connected with theslun't 'circuited conductors 3 and 4t. Leads 42 and 4-3 should begrounded. At the point B lead should be connected with theshort-circuited conductors 1 and 2,

and in like manner lead 41 should be connected with the short-circuitedconductors 3 and t. Leads 42 and 413' should be grounded at point B. Itwill be seen that current will flow from the oscillator 9 through thewindings of coil 5 over the conductors 1-2 and 3-4.'in parallel to thepoint B, thence through the leads and i1 and windings of coil 15 and ofpotentiometer 29, receiver 23 and thence over a grounded return to theoscillator 9. The switch 22 should he closed in its upper positionands-witch 2 L should be operated so as to apply current from source 9to the line. By moving the arm of potentiometer 29 until no tone isperceptible in the receiver 23, the magnitude of the unbalance existingin the phantom circuit may be determined.

"cuit such as L, may be determined.

In similar manner the magnitude of any unbalance existing in anon-phantomed cirl and 2 in parallel, and thence through the" halves ofwinding and potentiometer coil 29 to the receiver 23, and from thenceback to the source 9 through a grounded connection. By adjusting thepotentiometer 29 until no tone is perceptible in the receiver themagnitude of the unbalance may be determined. In this test, as in thepreceding one, the switch 22 should be closed in 1ts upper position andswitch 24L should likewise be operated.

It will be seen from the foregoing that the invention comprises portablemeans for accurately and eiiiciently determining the location of anunbalance in a circuit, which may be due to resistance, inductance orcapacity. It also provides means whereby the source of testing potentialis remotely controlled by the test man at the point where his receivingcircuit is connectedwvithv the circuit under test, so that such testingpotential will be applied to the line only for the minimum time requiredto make the test and only at those times when the circuits are idle,which is determined by the test man listening in at the point where hisreceiving device is located.

Although this invention has been described as having a certain form ofembodiment, it is apparent that it is capable of embodiment in other anddifferent forms without departing from the spirit and scope of the appended claims: 7

What is claimed is:

1. I11 an electrical testing system for locating irregularities in aline circuit, the combination of a line circuit, a source of varyingpotential, means for connecting, said source With the said line circuit,a measuring circuit having means for connecting it with the said linecircuit at a point remote from that at which the said source ofpotential is connected thereto and having associated therewith means fordetermining the nature and the magnitude of an irregularity existing-inthe said line circuit, and means associated with the said measuringcircuit to control the application of the potential to the said linecircuit.

2. In an electrical testing system for locating irregularities in a linecircuit, the combination with a phantom line circuit of In ora source ofalternating potential having means for connecting the said. Sourcewiththe said line circuit, a measuring circuit also having means forconnecting it with the said line circuit at a point remote from that.

balance measuring device having means to.

bridge it across the said line circuit at a point remote from the pointof connection of the said source with the said line circuit, and. meansassociated with the said measu1zing device to control the connection of.the said source of potential to the said line circuit.

4. In an electricattesting system, the coni-.

bination of a line circuit characterized by electrical unbalance, asource of testing potential having means-t0 bridge it across the saidline circuit, an unbalance measuring device having means to bridge itacross the said line circuit, and meansassociated with the saidmeasuring device tosetin-oper-ation and efiectively connect thesaidsource of testing potential to the line circuit.

5. In an electricaltesting system, the combination of two pairs of linewires, balanced retardation coils, means to bridge said coils across:the saidv pairs, switching means to connectv a source of testingpotential with the midpoint of each of said coils, and means associatedwith the said switching means to shunt the said retardation coils whenthe said source of potential is connected thereto.

6. In an electrical testing system, the combination of a source ofalternating current, a transmission line characterized by unbalancebetween conductors, balanced retardation coils, means to bridge the saidcoils across each. pair of said conductors, switch ing means to effectthe connection of the said alternating current source to the midpointsof the said retardation coils, a second group of coils,,means to connectsaid second group. of coils across the said pairs of conductors atapoint remote from the point of connection tothe said first retardationcoils and having a potentiometer associated with each, of said secondcoils, a current indicating device and switching means associatedtherewith, adapted to control the operation of the said first mentionedswitching means whereby the application of the alternating current maybe controlled from a point of the line remote from the source ofaltcrnating current.

In testimony whereof, I have signed my name tovthis specification thisfifth day of May 1921.

BENJAMIN H. BIRCHALL.

